Method for melting glass

ABSTRACT

The present invention is related to a method for the combustion of pulverized fuel as a heating source for melting raw materials for producing glass. The method including the steps of, feeding a regulated controlled flow of a mixture of pulverized fuel and air or gas under pressure for pneumatic transport in at least one distribution means; discharging the mixture of pulverized fuel and air or gas from feeding means toward at least one of said distribution means; regulating in a controlled manner the pulverized fuel-air or gas mixture from the distribution means to each of a plurality of burners in a glass melting region of a glass melting furnace; burning the pulverized fuel by means of the burners in the glass melting region of said glass melting furnace while providing a combustion flame with high thermal efficiency to carry out a controlled heating for melting the glass; and, counteracting erosive and abrasive effects of the pulverized fuel in the glass melting furnace by means of refractory materials. The refractory materials being selected of silica-alumina-zircon, magnesite, chrome-magnesite, magnesia-alumina spinel, alumina-silicate, zircon-silicate, magnesium oxide silica or alumina mixtures of the same.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a method for melting glass and, morespecifically to a method for melting glass using a pulverized fuel.

2. Related Prior Art

Melting glass has been done in different kinds of furnaces and usingdifferent types of fuels, depending on the final characteristics of theproduct and also with regard to the thermal efficiency of the meltingand refining processes. Unit melter furnaces have been used to meltglass (by means of gas fuel). These furnaces have several burners alongthe sides of the furnace, and the whole unit looks like a closed boxwhere there is a chimney that can be placed either in the beginning ofthe feeder or at the very end of the furnace, in other words, goingdownstream. However there is an enormous heat loss in the glass leavinghigh-temperature operating furnaces. At 2500° F., for example, the heatin the flue gases is 62 percent of the heat input for a natural gasfired furnace.

In order to take advantage of the remaining heat of the flue gases, amore sophisticated and expensive design came into being, named as theregenerative furnace. It is well known that, to operate a regenerativeglass melting furnace, a plurality of gas burners is associated with apair of sealed regenerators disposed side-by-side. Each regenerator hasa lower chamber, a refractory structure above the lower chamber and anupper chamber above the structure. Each regenerator has a respectiveport connecting the respective upper chamber with a melting and refiningchamber of the furnace. The burners are arranged to burn fuel, such asnatural gas, liquid petroleum, fuel oil or other gaseous or liquid fuelswhich are suitable for use in the glass melting furnace and therebysupply heat for melting and refining the glass making materials in thechamber. The melting and refining chamber is fed with glass makingmaterials at one end thereof at which is located a doghouse and has amolten distributor disposed at the other end thereof, which comprises aseries of ports through which molten glass may be removed from themelting and refining chamber.

The burners may be mounted in a number of possible configurations, forexample a through-port configuration, a side-port configuration or anunder-port configuration. Fuel, e.g. natural gas, is fed from the burnerinto the incoming stream of pre-heated air coming from each regeneratorduring the firing cycle, and the resultant flame and products ofcombustion produced in that flame extend across the surface of themelting glass, and transfer heat to that glass in the melting andrefining chamber.

In operation, the regenerators are cycled alternately between combustionair and exhaust heat cycles. Every 20 minutes, or 30 minutes, dependingon the specific furnaces, the path of the flame is reversed. Theobjective of each regenerator is to store the exhausted heat, whichallows a greater efficiency and a higher flame temperature that couldotherwise be the case with cold air.

For operating the glass melting furnace, the fuel fed to the burners andthe combustion air supplied is controlled by measuring at the port mouthand the top of the structure, the quantity of oxygen and combustiblematerial present so as to ensure that within the melting chamber or atpoints along the melting chamber, the combustion air fed is less thanthat required for complete combustion of the fuel being supplied.

In the past, the fuel used to melt glass was fuel oil, coming fromdistillation of petroleum. For many years this kind of fuel was used,but the tighten of environmental regulations have been pushing forreduction of fuel oil, since this kind of oil has impurities coming fromthe petroleum crude oil, such as, sulphur, vanadium, nickel, and someother heavy metals. This kind of fuel oil produce pollutants such asSOx, NOx and particulates. Recently the glass industry has been usednatural gas as a cleaner fuel. All the heavy metals and sulphur comingin the liquid stream of petroleum residuals from distillation are notcontained in natural gas. However, the high temperature produced in theflame of natural gas has been very effective for producing more NOx thanother pollutants. In this sense, a lot of effort has been done in orderto develop low NOx burners for firing natural gas. Additionally,different technologies have been developed to prevent the NOx formation.An example of this is the Oxy-fuel Technology, which utilizes oxygeninstead of air for the combustion process. This technology has theinconvenient of require a unit melter furnace with a special preparationof the refractories since air infiltration need to be prevented. The useof oxygen also produced a higher temperature flame, but with the absenceof nitrogen the NOx production is drastically reduced.

The other inconvenient of oxy-fuel process is the cost of the oxygenitself. In order to make it cheaper it needs to place an oxygen plantbesides the furnace in order to feed the required oxygen by the meltingprocess.

However, the continuing upward spiral of energy costs (primarily naturalgas) have forced the major float glass manufacturers to add “surcharges”to truckloads of flat glass. Natural gas prices have increased over 120%this year (in Mexico only or elsewre), far above previous estimates.

The general consensus among glass industry insiders is that distributorswill be forced to take a close look at these new ‘surcharges’, and mostlikely be forced to pass them along.

Taking into account the previous art, the present invention is relatedto the application of different technologies to reduce the melting cost,using a solid fuel coming from the petroleum residuals of distillationtowers, such as petroleum coke, in order to be used for glass productionin an environmentally clean way.

The main difference of this type of fuel regarding fuel oil and naturalgas is the physical state of the matter, since fuel oil is a liquidphase, natural gas is a gas phase while petroleum coke for instance is asolid. Fuel oil and petroleum coke have the same kinds of impurities,since both of them are coming from residuals of distillation tower ofcrude oil. The significant difference is the amount of impuritiescontained in each of these. Petroleum coke is produced in three types ofdifferent processes called delayed, fluid and flexi. The residuals fromthe distillation process are placed in drums and then heated up to from900.degree. to 1000° Fahrenheit degrees for up to 36 hours in order totake out most of the remaining volatiles from the residuals. Thevolatiles are extracted from the top of the coking drums and theremaining material in the drums is a hard rock make of around 90 percentof carbon and the rest of all the impurities from the crude oil used.The rock is extracted from the drums using hydraulic drills and waterpumps.

A typical composition of petroleum coke is given as follow: carbon about90%; hidrogen about 3%; nitrogen from about 2% to 4%; oxigen about 2%;sulphur from about 0.05% to 6%; and others about 1%.

Use of Petroleum Coke

Petroleum solid fuels have already been used in cement and steam powergeneration industries. According to the Pace Consultants Inc. the use ofpetroleum coke in years 1999 for cement and power generation werebetween 40% and 14% respectively.

In both industries, the burning of petroleum coke is used as a directfire system, in which the atmosphere produced by the combustion of thefuel is in direct contact with the product. In the case of cementproduction, a rotary kiln is needed in order to provide a thermalprofiled require by the product. In this rotary kiln, a shell of moltencement is always formed avoiding the direct contact of the combustiongases and flames with the refractories of the kiln, avoiding attackthereof. In this case, the calcined product (cement) absorbs thecombustion gases, avoiding the erosive and abrasive effects of vanadium,SO3 and NOx in the rotary kiln.

However, due to the high sulfur content and the presence of vanadium,petroleum coke as fuel is not commonly used as a fuel in the glassindustry, due to the negative effect negative on the structure of therefractories and to environmental problems.

Problems with the Refractories

The glass industry use several kinds of refractory materials, and mostof them are used to accomplish different functions, not only the thermalconditions but also the chemical resistance and mechanical erosion dueto the impurities contained by fossil fuels.

Using a fossil fuel as the main energy source represents an input to thefurnace of different kinds of heavy metals contained in the fuel, suchas: vanadium pentoxide, iron oxide, chromium oxide, cobalt, etc. In theprocess of combustion most of the heavy metals evaporate because of thelow vapor pressure of the metal oxide and the high temperature of themelting furnace.

The chemical characteristic of the flue gases coming out of the furnaceis mostly acid because of the high content of sulphur from the fossilfuel. Also the vanadium pentoxide presents an acid behavior such as thesulphur flue gases. Vanadium oxide is one of metals that represents asource of damage to basic refractories, because the acid behavior ofthis oxide in gaseous state. Is well known that the vanadium pentoxidereacts strongly with calcium oxide forming a dicalcium silicate at 1275°C.

The dicalcium silicate continues the damage to form a phase of merwiniteand the to monticelite and finally to forsterite, which reacting withvanadium pentoxide to form a low melting point of tricalcium vanadate.

The only way to reduce the damage caused to basic refractories is thereduction of the amount of calcium oxide in the main basic refractory inorder to avoid the production of dicalcium silicate that continuesreacting with vanadium pentoxide until the refractory may fail.

On the other hand, the main problem with the use of the petroleum cokeis related with the high sulfur and vanadium content, which have anegative effect on the structure of the refractories in the furnaces.The foremost requirement characteristics of a refractory is to withstandexposure to elevated temperature for extended periods of time. Inaddition it must be able to withstand sudden changes in temperature,resist the erosive action of molten glass, the corrosive action ofgases, and the abrasive forces of particles in the atmosphere.

The effect of the vanadium on the refractories has been studied indifferent the papers, i.e. Roy W. Brown and Karl H. Sandmeyer in thepaper “Sodium Vanadate's effect on superstructure refractories”, Part Iand Part II, The Glass Industry Magazine, November and December 1978issues. In this paper the investigators tested different castrefractories which were centered on overcoming the vanadium attack inthe flowing cast compositions, such as alumina-zirconia-silica (AZS),alpha-beta alumina, alpha alumina and beta alumina, which are commonlyused in glass tank superstructures.

J. R. Mclaren and H. M. Richardson in the paper “The action of VanadiumPentoxide on Aluminum Silicate Refractories” describe a series ofexperiments in which cone deformation were carried out on sets of groundsamples from bricks with alumina content of 73%, 42% and 9%, each samplecontaining admixtures of vanadium pentoxide, alone or in combinationwith sodium oxide or calcium oxide.

The discussion of the results were focused on the action of VanadiumPentoxide, the action of Vanadium Pentoxide with Sodium Oxide and theAction of Vanadium Pentoxide with Calcium oxide. They concluded that:

1.—Mullite resisted the action of vanadium pentoxide at temperatures upto 1700° C.

2.—No evidence was found of the formation of crystalline compounds orsolid solutions of vanadium pentoxide and alumina or of vanadiumpentoxide and silica.

3.—Vanadium pentoxide may act as a mineralizer during the slagging ofalumino-silicate refractories by oil ash, but it is not a major salggingagent.

4.—Low-melting compounds are formed between vanadium pentoxide andsodium or calcium oxides, specially the former.

5.—In reactions between either sodium or calcium vanadates andalumino-silicates, lower-melting-point slags are formed with bricks highin silica than with bricks highs in alumina.

T. S. Busby and M. Carter in the paper “The effect of SO.sub.3,Na.sub.2SO.sub.4 and V.sub.20.sub.5 on the bonding minerals of basicrefractories”, Glass Technology Vol. 20, No. April, 1979, tested anumber of spinels and silicates, the bond minerals of basicrefractories, in a sulphurous atmosphere between 600 and 1400.degree.C., both with and without additions of Na.sub.2SO.sub.4 andV.sub.20.sub.5. It was found that some MgO or CaO in these minerals wasconverted to the sulphate. The reaction rate was increased by thepresence of Na.sub.2SO.sub.4 or V.sub.2O.sub.5. Their results indicatethat the CaO and MgO in basic refractories can be converted to thesulphate if they are used in a furnace where sulphur is present in thewaste gases. The formation of calcium sulphate occurs below 1400° C. andthat of magnesium sulphate below about 1100° C.

However, as was described of the above, the effect of the vanadium onthe refractories produce a great amount of problems in the glassfurnaces, which has not solved in its totality

Petroleum Coke and the Environment

Another problem of the use of the petroleum coke is related with theenvironment. The high content of sulphur and metals as nickel andvanadium produced by the combustion of the petroleum coke have provokedenvironmental problems. However, already exist developments for reduceor desulphurate the petroleum coke with a high content of sulphur (over5% by weight). For example, the U.S. Pat. No. 4,389,388 issued toCharles P. Goforth on Jun. 21, 1983, concerns to the desulfurization ofpetroleum coke. Petroleum coke is processed to reduce the sulfurcontent. Ground coke is contacted with hot hydrogen, under pressurizedconditions, for a residence time of about 2 to 60 seconds. Thedesulfurized coke is suitable for metallurgical or electrode uses.

U.S. Pat. No. 4,857,284 issued to Rolf Hauk on Aug. 15, 1989, is relatedto a process for removing sulphur from the waste gas of a reductionshaft furnace. In this patent, there is described a novel process forremoving the sulphur contained in a gaseous compound by absorption fromat least part of the waste gas of a reduction shaft furnace for ironore. The waste gas is initially cleaned in a scrubber and cooled,followed by desulphurization, during which the sulphur-absorbingmaterial is constituted by part of the sponge iron produced in thereduction shaft furnace. Desulphurization advantageously takes place ata temperature in the range 30° C. to 60° C. It is preferably carried outon the CO2 separated from the blast furnace gas and the blast furnacegas part used as export gas.

The U.S. Pat. No. 4,894,122 issued to Arturo Lazcano-Navarro, et al, onJan. 16, 1990, is related to a process for the desulphurization ofresiduals of petroleum distillation in the form of coke particles havingan initial sulphur content greater than about 5% by weight.Desulphurization is effected by means of a continuous electrothermalprocess based on a plurality of sequentially connected fluidized bedsinto which the coke particles are successively introduced. The necessaryheat generation to desulphurize the coke particles is obtained by usingthe coke particles as an electrical resistance in each fluidized bed byproviding a pair of electrodes that extend into the fluidized cokeparticles and passing an electrical current through the electrodes andthrough the fluidized coke particles. A last fluidized bed withoutelectrodes is provided for cooling the desulphurized coke particlesafter the sulphur level has been reduced to less than about 1% byweight.

The U.S. Pat. No. 5,259,864 issued to Richard B. Greenwalt on Nov. 9,1993, is related to a method for both disposing of an environmentallyundesirable material comprising petroleum coke and the sulfur and heavymetals contained therein and of providing fuel for a process of makingmolten iron or steel preproducts and reduction gas in a melter gasifierhaving an upper fuel charging end, a reduction gas discharging end, alower molten metal and slag collection end, and means providing an entryfor charging ferrous material into the melter gasifier; introducingpetroleum coke into the melter gasifier at the upper fuel charging end;blowing oxygen-containing gas into the petroleum coke to form at least afirst fluidized bed of coke particles from the petroleum coke;introducing ferrous material into the melter gasifier through the entrymeans, reacting petroleum coke, oxygen and particulate ferrous materialto combust the major portion of the petroleum coke to produce reductiongas and molten iron or steel preproducts containing heavy metals freedfrom combustion of the petroleum coke and a slag containing sulfur freedfrom combustion of the petroleum coke.

An additional factor to be considered in the glass industry is thecontrol of the environment mainly the air pollution. The melting furnacecontributes over 99% of both particulates and gaseous pollutants of thetotal emissions from a glass plant. The fuel waste gas from glassmelting furnaces consists mainly of carbon dioxide, nitrogen, watervapour, sulphur oxides and nitrogen oxides. The waste gases releasedfrom melting furnaces consist mainly of combustion gases generated byfuels and of gases arising from the melting of the batch, which in turndepends on chemical reactions taking place within this time. Theproportion of batch gases from exclusively flame-heated furnacesrepresents 3 to 5% of the total gas volume.

The proportion of the air-polluting components in the fuel waste gasdepends on the type of the firing fuel, its heating value, thecombustion air temperature, the burner design, the flame configuration,and the excess of air supply. The sulphur oxides in the waste gases ofglass melting furnaces originated from the fuel used, as well as fromthe molten batches.

Various mechanisms have been proposed that include volatilization ofthese metal oxides and as hydroxides. Whatever the case, it is wellknown as the result of chemical analysis of the actual particulatematter, that more than 70% of the materials are sodium compounds, about10% to 15% are calcium compounds, and the balance are mostly magnesium,iron, silica and alumina.

Another important consideration in the glass melting furnace is theemission of SO.sub.2. The emission of SO.sub.2 is a function of thesulfur introduced in the raw materials and fuel. During the time offurnace heating such as after a rise in production level, an abundanceof SO.sub.2 is given off. The emissions rate of SO.sub.2 ranges fromabout 2.5 pounds per ton of glass melted to up to 5 pounds per ton. Theconcentration of SO.sub.2 in the exhaust is generally in the 100 to 300ppm range for melting with natural gas. While using high sulfur fuel,approximately 4 pounds of SO.sub.2 per ton of glass for every 1% ofsulfur in the fuel is added.

On the other hand, the formation of NOx as result of combustionprocesses has been studied and described by a number of authors(Zeldovich, J. The oxidation of Nitrogen in Combustion and explosions.Acta. Physiochem. 21 (4) 1946; Edwards, J. B. Combustion: The formationand emissions of trace species. Ann Arbor Science Publishers, 1974.p-39). These were recognized and by the Emissions Standards Division,Office of Air Quality Planning and Standards, USEPA, in their report on“NOx Emissions from glass manufacturing” include Zeldovich onhomogeneous NOx formation and Edwards with his presentation of empiricalecuations. Zeldovich developed rate constants for the formation of NOand NO.sub.2 as the result of high temperature combustion processes.

Finally under normal operating condition, where flames are adjustedproperly and the furnace is not starved for combustible air, very littleCO or other residuals from incomplete combustion of fossil fuel arefound in the exhaust. The gas concentration of these species will beless than 100 ppm, probably lower than 50 ppm, with a production rate ofless than 0.2%/ton. The control for these pollutants is simply a propercombustion set up.

Processing techniques for the reduction of gaseous emissions areessentially restricted to the proper selection of firing fuels and rawmaterials, as well as to furnace design and operation. The U.S. Pat. No.5,053,210 issued to Michael Buxel et al, on Oct. 1, 1991, describes amethod and apparatus for the purification of flue gases, particularlyfor the desulphurization of and NO.sub.x-elimination from flue gas bymultistage adsorption and catalytic reaction in gravity-flow moving bedsof granular, carbon-bearing materials contacted by a transverse steam ofthe gas, in which a minimum of two moving beds are arranged in serieswith reference to the gas route so that NO.sub.x-elimination takes placein the second or any downstream moving bed. Where large volumes of fluegas from industrial furnaces must be purified, purification is adverselyaffected by the formation of gas streaks with widely varying sulphurdioxide concentrations. This disadvantage is eliminated in that theprepurified flue gas leaving the first moving bed and having a locallyvariable sulphur dioxide concentration gradient is subjected to repeatedmixing before ammonia is added as reactant for NO.sub.x-elimination.

The U.S. Pat. No. 5,636,240 issued to Jeng-Syan et al, on Jun. 3, 1997,is related to an air pollution control process and apparatus for glassfurnaces for use in the furnace's waste gas outlet including passing thewaste gases through a spray type neutralization tower to removesulphates in the waste gases by spraying an absorbent (NaOH) to reducethe opacity of exhaust gas, and employing a pneumatic powder feedingdevice to feed flyash or calcium hydroxide periodically in a pathbetween the spray type neutralization tower and a bag house to maintainnormal functioning of the filter bag in the bag house.

Burners for Pulverized Fuel

Finally, for the burning of pulverized or dust petroleum coke isnecessary to consider a special type of burner design. Generally,ignition energy is supplied to a combustible fuel-air mixture forigniting the burner flame. Some burner systems have been developed toburn pulverized fuel as coal o petroleum coke. PCT applicationPCT/EP83/00036 of Uwe Wiedmann et al, published on Sep. 1, 1983,describes a burner for pulvurulent, gaseous and/or liquid fuels. Thisburner has an ignition chamber with a wall, which opens out and havingthe rotation symmetry, as well as an exhaust pipe connected thereto. Atthe center of the chamber wall, there is arranged the inlet of a pipefor the admission of a fuel jet as well as an air supply surroundingsaid inlet for the admission of a vortex of combustion air whichproduces, inside the ignition chamber, a hot recirculation stream mixingthe fuel jet and heating the latter at the ignition temperature. The airquantity of the vortex supplied to the ignition chamber is only aportion of the total combustion air required. In the area between thechamber wall and the exhaust pipe there is provided a second airadmission pipe through which another portion of the combustion air maybe introduced in the ignition chamber, said portion being totally orpartially mixed with the fuel jet. The sum of the combustion airportions participating within the ignition chamber to the mixture withthe fuel jet (an hence to the ignition and initiation of the combustion)is adjusted so as not exceed 50% of the total combustion air required.By conjugating all those measures, there is provided a burnerparticularly appropriate for the production of heat for industrialprocess and further having at intermediary and variable power rates astable ignition producing a flame with an elongate and thin form in thecombustion chamber and thus with a low radial deflection of particles.

The U.S. Pat. No. 4,412,810 issued to Akira Izuha et al, on Nov. 1,1983, is related to a pulverized coal burner capable of carrying outcombustion in a stable state with a reduction in the amounts of NOx, Co,and unburned carbon produced as the result of the combustion.

The U.S. Pat. No. 4,531,461 issued to William H. Sayler on Jul. 30,1985, is related to a system for pulverizing and burning solid fuel,such as coal or other fossil fuel, and for burning such pulverized fuelssuspended in a stream of air, principally in connection with industrialfurnaces such as those used to heat gypsum-processing kettles andmetallurgical furnaces.

The U.S. Pat. No. 4,602,575 issued to Klaus Grethe on Jul. 29, 1986, isrelated a Method of burning petroleum coke dust in a burner flame havingan intensive internal recirculation zone. The petroleum coke dust issupplied to that region of the intensive recirculation zone whichprovided the ignition energy for the petroleum coke dust which is to beburned. However, this patent describes that, depending upon the type ofprocessing which the crude oil has undergone, the petroleum coke cancontain harmful materials such as, vanadium which not only lead tocorrosive compounds during combustion in steam generators, butfurthermore considerably pollute the environment when they leave the“steam generator” with the flue gas. Suggest that, when this burner isused, these negatives effects or harmful occurrences can be extensivelyavoided by adding vanadium-binding additives to the combustion via theincremental of air.

Another development on coal burners is illustrated in the U.S. Pat. No.4,924,784 issued to Dennis R. Lennon et al, on May 15, 1990, which isrelated to the Firing of pulverized solvent refined coal in a burner fora “boiler or the like”. Finally, the U.S. Pat. No. 5,829,367 issued toHideaki Ohta et al, on Nov. 3, 1998, is related a burner for combustionof a pulverized coal mixture having two kinds of rich and leanconcentration has a height of a burner panel of a burner panel reducedand the overall burner simplified. The burners applied for a boilerfurnace or a chemical industrial furnace.

As has been described above, the developments have been focused tocontrol the pollution of the petroleum coke, however, these have beenfocused on the desulphurization or decontamination of the petroleumcoke.

On the other hand, notwithstanding that the petroleum coke has alreadybeen used in other industries, in some cases the same product absorbsthe pollution gases, as well, the erosive and abrasive effects ofvanadium on the furnaces (see cement industry).

In each case, the pollution problems and their solution depend on eachindustry. Each industry and furnaces have different thermal propertiesand problems with contaminants, with the type of refractories—which alsoinfluence energy consumption and product quality—, and over the furnacestructure and over the product resultant.

Notwithstanding the foregoing, the glass industry has to date notconsidered the burning of petroleum coke for the melting of glass rawmaterials due to the consideration of all the factors above described,such as pollution and the high sulfur and vanadium contents, which havea negative effect on the structure of the refractories in the furnacesand also serious problems with the environment.

Considering all the processes described above, the present invention isrelated with the use of a low cost solid fuel, from petroleumdistillation residual (petroleum coke) in order to produce commercialglass in an environmentally clean way, reducing the risk of damage inthe refractories of the glass furnace and reducing the emissions ofcontaminant in the atmosphere. This solid fuel, as was described in therelated art, has not previously been considered for use in the meltingof glass materials because of the problems previously described.

In order to utilize of this invention effectively, combustion equipmentfor feeding and burning petroleum coke was developed in order to performan efficient combustion. The invention also contemplates an emissionscontrol system, which was located following the furnace in order toclean the flue gases to avoid the emission of impurities from the fuel,such as SOx, NOx and particulates. By the integration of developedequipment, selecting the right configuration of equipment and systems,it is possible to use a low cost fuel, produce commercial glass andgenerate flue gases within environmental regulations.

From the above, the present invention lies in the design of severalsystems placed in a single process in order to produce commercial glassin a side-port type glass furnace. So, in a glass melting furnace ofside-port type, pulverized fuel of type composed of carbon, sulfur,nitrogen, vanadium, iron and nickel is burned for melting glass rawmaterials for the manufacture of glass sheets or containers. Means forsupplying the pulverized fuel are fed in at least a burner that isarranged by each one of a plurality of first and second side ports of aglass melting region of said glass melting furnace, for burning thepulverized fuel during cycles of melting glass, said glass meltingfurnace including refractory means at regenerative chambers of a glassmelting furnace for resisting the erosive action of the melting glass,the corrosive action of combustion gases and the abrasive forces ofparticles in the atmosphere provoked by the burning of said pulverizedfuel in the furnace. Finally, means for controlling the air pollution ina waste gas outlet after that the combustion of the pulverized fuel inthe glass melting furnace has been carried out, said means forcontrolling the air pollution reducing the emissions of sulfur, nitrogenvanadium, iron and nickel compounds at the atmosphere.

Furthermore, in order to reduce or avoid possible damage due tomagnesium oxide, it is required to have at least a 98% of magnesiumoxide where the purity of the raw materials forming the refractoryreducing the amount of calcium oxide present in the material andretarding the formation of a molten phase. This refractory in order tohave the impurities surrounded by magnesium oxide must be sintered athigh temperature created a ceramic bond in the main material.

The basic refractory of 98% of magnesium oxide or greater is mostly usedin the top rows of the regenerative chambers of the glass furnace.Another example of refractories that can be used in the regenerativechambers or top checkers where the Zircon-silica-alumina fused castmaterials which also present an acid behavior as the vanadium pentoxidereducing the impact of damage to the refractories.

The right selection of refractory material within the glass furnace canreduce the impact of the impurities contained in the fossil fuel, basedon the thermodynamical analysis and the chemical composition of theimpurities and the chemical compounds forming the refractories.

That invention has been described in relation with a specific type offurnaces. However, it has been found that by using the actual burners,it was necessary the use of a second air to be mixed with the pulverizedfuel-air or gas mixture, all of which produces a lost of heat during thecombustion cycle, and by consequence the efficiency of the burners isreduced.

Applicants consider that the above lost of heat is due a the entrance ofcold air used for cooling reasons, and consequently the consumption ofpulverized fuel is slightly increased, producing more CO gases thatresults after the combustion.

SUMMARY OF THE INVENTION

In accordance with the present invention a first objective of thepresent invention is to provide a method for melting glass for supplyingin a controlled manner a pulverized fuel-air or gas mixture to each of aplurality of burners in a glass melting region of the glass meltingfurnace for operating said burners in alternate operating cycles betweencombustion and non-combustion cycles.

Is an additional objective of the present invention to provide a methodfor melting glass, which reduces the costs of melting.

An additional objective of the present invention is to provide a methodfor melting glass which produces an optimal mixture between thepulverized fuel-air or gas mixture, reducing the gases CO that resultsof the combustion.

It is other advantage of the present invention to provide a method formelting glass wherein the erosive and abrasive effects of the pulverizedfuel in the glass melting furnace are diminished.

It is another objective of the present invention to provide a method formelting glass, wherein a mix of pulverized fuel in combination withprimary air or gas is injected at high velocity in each one of theburners.

An additional object of the present invention is to provide a method formelting glass, which uses special refractories for the construction ofthe chambers of the glass melting furnace with the object of diminishthe erosive and abrasive effects produced by the burning of saidpulverized fuel, specially by the effects produced by the V.sub.2O.sub.5, Fe.sub.2.O.sub.3., Fe.O, and Ni.O. that are metals included ascontaminants in the solid fuel.

An additional objective of the present invention to provide a method formelting glass wherein pulverized fuel is fed directly to a glass meltingfurnace in a relation fuel-air of about 16% of air in excess withrespect to a stoichiometric air.

Another objective of the present invention is to provide a method formelting glass in a glass melting furnace, which also can besimultaneously melted with two or three types of fuel. Series of burnerscan be arranged in the melting chamber for burning independentlypetroleum coke, gas or fuel oil.

Other objective of the present invention is to provide a method formelting glass, wherein the pulverized fuel is fed by means of pneumaticmeans, with a elevated relation solid-air.

These and other objectives and disadvantages of the present inventionwill be evident to the experts in the field from the following detaileddescription of the invention, which is illustrated in the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an embodiment of the present invention,comprising mainly: a system for feeding and burning a pulverized fuel inat least a burner of a glass melting furnace; refractory means indifferent shapes, forming the walls and floor of a glass melting furnacefor resisting the erosive action of the melting glass, the corrosiveaction of combustion gases and the abrasive forces of particles in theatmosphere provoked by the burning of said pulverized fuel in thefurnace; and a environmental control system for controlling the airpollution in a waste gas outlet after that the combustion of thepulverized fuel as been carried out in the furnace.

FIG. 2 illustrate another block diagram of a first embodiment of thesystem for feeding and burning the petroleum coke in accordance with thepresent invention.

FIG. 3 is a plant view of a regenerative-type glass melting furnace;

FIG. 4 is a schematic longitudinal view of the furnace illustrated inFIG. 1;

FIG. 5 is a schematic view of the system for feeding and burning apulverized fuel in accordance with the present invention;

FIG. 6 is a lateral view of the system for feeding and burning apulverized fuel in combination with the regenerative-type glass meltingfurnace;

FIG. 7 is a detailed view of an arrangement of a burner for feeding andburning a pulverized fuel in accordance with the present invention;

FIG. 8 is a side view, which is taking of FIG. 7, in a preferredembodiment of a burner for burning pulverized petroleum coke inaccordance with the present invention;

FIG. 9 is a front view, which is taking of FIG. 8;

FIG. 10 is a detailed view of a vertical section of the burner of FIG.8, showing a burner in accordance with the present invention; and,

FIG. 11 is plant view taken along the line “A-A” of FIG. 10, showing theburner with two exit nozzles.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now described in relation to a specific embodiment,wherein the same parts will be referred to the same numbers and whereinthe FIG. 1 is a block diagram of an embodiment of the present invention,comprising mainly: a system for feeding and burning a pulverized fuel inat least a burner A of a glass melting furnace, of the type side-port,as will be describe later. Refractory means B formed in differentshapes, for forming the walls, floor, roof of a glass melting furnace,walls, floor and roof of the different combustion ports where the burneror burners are positioned, and the walls, roof and empilage of checkersof the regenerator chambers, the refractory means being selected ofsilica, alumina, zircon, magnesite, chrome, ceramic, alumina-silicate,zircon-silicate, magnesium oxide or mixtures of the same. For example,said refractory materials being manufactured of: pressed silica, fusedsilica, direct-cast silica; fused-cast alumina-silica-zircon; pressedalumina-silica-zircon or direct-cast alumina-silica-zircon; fused-castalumina (90-100%), pressed alumina (90-100%), direct-cast alumina(90-100%); fused-cast Magnesite-alumina spinel, press magnesite-aluminaspinel, direct-cast magnesite-alumina spinel; fused-castmagnesite-zircon-silica, pressed magnesite-zircon-silica, direct-castmagnesite-zircon-silica; fused-cast alumina-silicate, pressedalumina-silicate, direct-cast alumina-silicate; fused-castzircon-silicate, pressed zircon-silicate, direct-cast zircon-silicate;pressed direct bonding 98% magnesium oxide, pressed ceramic bonding 98%magnesium oxide, direct-cast 98% magnesium oxide; pressed direct bonding90-95% magnesium oxide; pressed ceramic bonding 90-95% magnesium oxide;direct-cast 90-95% magnesium oxide; pressed direct bonding chrome(5-25%)-magnesite (50-85%); pressed ceramic bonding chrome(5-25%)-magnesite (50-85%); or direct-cast chrome (5-25%)-magnesite(50-85%).

Other materials that can be used in the walls, roof and floor of theglass melting furnaces where the temperatures are as high as 1350 to1450 celsius are the Zircon-silica-alumina fused cast materials whichalso present an acid behavior as the vanadium pentoxide reducing theimpact of damage to the refractories. Another type of the refractorymaterials that can be used are those selected of a material containingof about of 80% magnesia and about 20% zirconium-silicate. Saidmaterials being used for resisting the erosive forces of the meltingglass, the corrosive action of combustion gases and the abrasive forcesof particles in the atmosphere provoked by the burning of the pulverizedfuel (petroleum coke) in the furnace. Finally, an environmental controlsystem C is required for controlling the air pollution in a waste gasoutlet after that the combustion of the pulverized fuel as been carriedout in the furnace.

Different materials can be properly used in the melter of glass furnaceto operate with pulverized fuel, such as petroleum coke that has beendescribed in the present invention. In the case of sidewalls, andfurnace breastwalls fused-cast or direct-cast Alumina-zircon-silicamaterials have been used to provide chemical resistance to glass, carryover and alkali volatilization and heavy metals contaminants ofpulverized fuels. Also the last ports of side-port furnaces where carryover is not found since the batch and foam is already melted, othermaterials such high alumina can be used. The process of manufacture thedifferent materials could be fused-cast, pressed or direct-casting. Alsohigh alumina and low calcium content will increase the chemicalresistance of refractories reducing the chemical reaction of heavymetals such as vanadium with calcium silicates of bonding agents used inrefractories. In refiner areas of melter, where there are no flames,silica products are suitable for breastwalls and furnace front and gablewalls. In the case of ports, they can be made of walls, floors and crownof ports, alumina-zircon-silica, high alumina, magnesia-alumina spinelrefractories can be used.

It must be understood that different processes of manufacturerefractories can be applied such as fused-cast, pressed molds anddirect-casting, depending upon the suitable materials for doing so.

In the case of walls, and crown of top regenerators, different materialsare also suitable for working with such heavy metals as found inpulverized fuel, such as, petroleum coke, chrome-magnesite, magnesite,and magnesite-zircon-silicate materials provide good chemicalresistance. Silica is often used in crown regenerators and it is alsorecommended.

For top checkers, Alumina-zircon-silica fused cast materials, as well asmagnesite, chrome-magnesite, magnesite-zircon-silicate are consideredsuitable and chemical stable to deal with all the different chemicalcompounds that come from the glass operation as well as with the heavymetals of pulverized fuels, such as petroleum coke.

For lower checkers where temperature is lower and chemical environmentis less aggressive, the following refractories are considered convenientto operate: pressed direct bonding 98% magnesium oxide, pressed ceramicbonding 98% magnesium oxide, direct-cast 98% magnesium oxide; presseddirect bonding 90-95% magnesium oxide; pressed ceramic bonding 90-95%magnesium oxide; direct-cast 90-95% magnesium oxide; pressed directbonding chrome (5-25%)-magnesite (50-85%); pressed ceramic bondingchrome (5-25%)-magnesite (50-85%); or direct-cast chrome(5-25%)-magnesite (50-85%).

Now making reference to FIG. 2, the system for feeding and burning apulverized fuel (A) will be connected to each burners 48 a, 48 b, 48 c,48 d 48 e, 48 f, 48 g and 48 h, as well as, to each burners 50 a, 50 b,50 c, 50 d, 50 e, 50 f, 50 g and 50 h (see FIGS. 3 and 5) for feedingand burning the pulverized petroleum coke within the glass meltingfurnace. The system for feeding and burning a pulverized fuel (A)comprises in combination; a dosing system (D) for dosing the pulverizedpetroleum coke and, a combustion system (E) for burning the pulverizedpetroleum coke within the glass melting furnace. The dosing system (D)can be fed by a system for feeding and handling the pulverized petroleumcoke (F), already known in the industry.

The system for feeding and burning a pulverized fuel (A) will now bedescribed in relation to FIGS. 3 through 5, i.e. the FIGS. 3 and 4 areshowing schematic views of a regenerative-type glass melting furnacewhich comprises a melting chamber 10, a refining chamber 12, aconditioning chamber 14 and a throat 16 between the refining chamber 12and the conditioning chamber 14. At a front end 18 of the refiningchamber 12 comprises a series of forehearth connections 20 through whichmolten glass is removed from the refining chamber 12. The rear end 22 ofthe melting chamber 10 including a dog house 24 through which glassmaking materials are fed by means of a batch charger 26. A pair ofregenerators 28, 30 are provided by each side of the melting chamber 10.The regenerators 28 and 30 are provided with firing ports 32, 34,connecting each regenerator 28, 30, with the melting chamber 10. Theregenerators 28, 30 are provided with a gas regenerator chamber 36 andan air regenerator chamber 38. Both chambers 36 and 38 are connected toa lower chamber 40, which is arranged to be communicated by means ofdampers 42 toward a tunnel 44 and a chimney 46 for the exhaust gases.Burners 48 a, 48 b, 48 c, 48 d 48 e, 48 f, 48 g and 48 h, as well asburners 50 a, 50 b, 50 c, 50 e, 50 f, 50 g and 50 h are arranged by eachport 32, 34, in a neck portion 52, 54, of each firing ports 32, 34 inorder to burn fuel, as natural gas, petroleum coke or other type offuels for use in the glass melting furnace.

Thus, when the glass making materials are fed through the dog house 24in the rear end of the melting chamber 10, the melting glass is meltedby the burners 48 a-h, 50 a-h, and floats in a forward direction untilcompletely melting to pass from the melting chamber 10 to theconditioning chamber 14. During the operation of the furnace, theregenerators 28, 30 are cycled alternately between combustion air andexhaust cycles. Every 20 minutes, or 30 minutes, depending on thespecific furnaces, the path of the flame of a series of burners 48 a-hor 50 a-h are reversed. So, the resultant flame and products ofcombustion produced in each burner 48 a-h, 50 a-h, pass across thesurface of the melting glass, and transfer heat to that glass in themelting chamber 10 and refining chamber 12.

Feeding the Pulverized Petroleum Coke (F)

Making now reference to FIGS. 5 and 6, the system for feeding andburning a pulverized fuel (A) in a glass melting furnace comprises in afirst embodiment of the present invention, first storage silos or tanks56 and 58 for storing pulverized petroleum coke or other types of fuelfor use in the glass melting furnace. The storage silos 56, 58 are fedthrough a wagon or wagon train 60 by means of a first inlet pipe 62connected between the wagon train 60 and the silos 56,58. The first mainpipe 62 having first branch pipes 64, 66, which are connectedrespectively to each silo 56,58, for the filling of each silo 56,58.Valves 68, 70 are connected to each first branch pipe 64 and 66 toregulate the filling of each silo 56, 58. Each silo 56, 58 are filled bymeans of a vacuum effect through of a vacuum pump 70 by means of a firstoutlet pipe 72. The first outlet pipe 72 having second branch pipes 74,76, to be connected with each silo 56,58. Valves 78, 80 are connected byeach second branch pipes 74, 76, to regulate the vacuum effect providedby the vacuum pump 70 for the filling of each silo 56, 58.

At the bottom of each silo 56, 58, a conical section 82, 84, and agravimetric coke feeding system 86, 88, are included for fluidizing andfor assuring a constant discharge flow of the pulverized coke into asecond outlet pipe 90 where the pulverized material is forwarded to asolid fuel dosing system SD-5, SD-6 and SD-7. The second outlet pipe 90including a third branch pipes 92, 94, connected to the bottom of eachconical section 82, 84 of each silo or tank 56, 58. Valves 96, 98, areattached to each third branch pipe 92, 94, to regulate the flow of thepulverized petroleum coke to the second outlet pipe 90.

Dosing System (D) for the Pulverized Petroleum Coke

Making now reference to the dosing system (D) in accordance with thepresent invention, the pulverized petroleum coke is received in eachsolid fuel dosing system SD-5, SD-6 and SD-7 through the second outletpipe 90. Fourth branch pipes 100, 102 and 104, are connected to thesecond outlet pipe 90, in order to transport the pulverized coke of thefirst silos or tanks 56 and 58 toward the solid fuel feeding systemSD-5, SD-6 and SD-7. Each solid fuel feeding system SD-5, SD-6 and SD-7,includes a second series of silos or tanks 106, 108, 110. The secondseries of silos 106, 108, 110, comprising a conical section 112, 114,116; a gravimetric coke feeding system 118, 120, 122; an aeration system124, 126, 128; a feeder 130, 132, 134; and a filter 136, 138 and 140,for discharging a constant flow of the pulverized coke toward each oneof the burners 48 f, 48 g, 48 h and burners 50 f, 50 g and 50 h, as willbe described later.

A pneumatic air compressor 142 and an air tank 144 are connected bymeans of a second main pipe 146. A first inlet branch pipes 148, 150,152, are connected with the second main pipe 146 for supplying afiltered air—through of the filters 136, 138 and 140—to transport thecoke toward the interior of each second series of silos or tanks 106,108, 110. The second main pipe 146 also includes a first return branchpipes 154, 156, 158, that are connected with each aeration system 124,126, 128, for permitting an adequate flow of the coke toward a thirdoutlet pipes 160, 162, 164, as will described later. Additionally, asecond inlet pipe 166 is connected with the second main pipe 146—afterthe air tank 144—which includes second inlet branch pipes 168, 170, thatare connected on the upper part of each silo or tank 56, 58, forinjecting air toward the interior of each silo or tank 56, 58.

The solid fuel feeding system SD-5, SD-6 and SD-7 including fourthoutlet pipes 172, 174, 176, connected below of each feeder 130, 132,134. A three-way regulatory valve 178, 180, 182, is connectedrespectively with the fourth outlet pipes 172, 174, 176, through a firstway; a second way is connected with first return pipes 179, 181, 183,for returning the excess of pulverized coke toward each second series ofsilos or tanks 106, 108, 110, whereas the third way is connected withthe third outlet pipes 160, 162, 164, which are used to supply anair-fuel mixture toward an arrangement of a four-way pipe 184, 186 and188 related with the combustion system (E) as be now described.

Combustion System (E)

Making reference now to the combustion system (E), it is connected toeach solid fuel feeding system SD-5, SD-6 and SD-7 through a first wayof the four-way pipe 184, 186 and 188, which are connected with eachthird outlet pipes 160, 162, 164 of each solid fuel feeding system SD-5,SD-6 and SD-7. A second way is connected, respectively, with fourthoutlet pipes 190, 192, 194, for feeding the supply of air-fuel mixturetoward the burners 48 h, 48 g and 48 f. A third way of the four-way pipe184, 186 and 188, is connected to fifth outlet pipes 196, 198, 200 forfeeding the air-fuel mixture toward the burners 50 h, 50 g and 50 f; anda fourth outlet of the four-way pipe 184, 186, 188 is connected,respectively, to second return pipes 202, 204, 206, for returning theair-fuel mixture back to each of the second series of silos or tanks106, 108, 110. The four-way pipe 184, 186 and 188 having ball valves 208A to C, 210 A to C, 212 A to C, between a connecting portion of thefour-way pipe 184, 186 and 188 and the fourth outlet pipes 190, 192,194; the fifth outlet pipes 196, 198, 200; and the second return pipes202, 204, 206.

Accordingly, in this manner, during the operation of the furnace, theburners 48 a-to-h or 50 a-to-h are cycled alternately between combustionand non-combustion cycles. Every 20 minutes, or 30 minutes, depending onthe specific furnaces, the path of the flame of a series of burners 48a-to-h or 50 a-to-h are reversed. The air-fuel mixture that is arrivingthrough the third outlet pipes 160, 162, 164, is regulated by thefour-way pipe 184, 186 and 188 and ball valves 208 A-to-C, 210 A-to-C,212 A-to-C, for alternating the injection of the air-fuel mixturebetween the burners 48 a-to-h and 50 a-to-h. When the alternateoperating cycle between the burners 48 a-to-h and 50 a-to-h is carriedout, the air-fuel mixture is returned back to the second series of silosor tanks 106, 108, 110 by means of the second return pipes 202, 204,206.

The air that is supplied through the third outlet pipes 160, 162, 164,is used for transporting the petroleum coke and for provoking highvelocities of coke injection toward the nozzle of each burner 48 a-to-hand 50 a-to-h. The air is supplied by means of a pneumatic air blower214 through a third main pipe 216.

Fourth outlet pipes 218, 220 and 222 are connected with the third mainpipe 216 and the third outlet pipes 160, 162, 164, for maintaining anelevated relation of the fuel-air mixture that is being supplied to theburners 48 a-to-h and 50 a-to-h.

For effectuating the combustion cycle of the burners 48 a-to-h or 50a-to-h, each burner 48 a-to-h or 50 a-to-h are fed individually with theair-fuel mixture. This mixture is supplied through an internal tube ofeach burner 48 a-h or 50 a-h, and arrives at a distribution chamber tobe distributed to the diverse injection nozzles of each burner 48 a-h or50 a-h.

For increasing the turbulence of the flows and the mixture of thepulverized fuel with a pre-heated combustion air in each burner 48 a-hor 50 a-h, a primary air supply is injected from a primary air blower224, which is supplied under pressure through the injection nozzles ofeach burner 48 a-h or 50 a-h, so that the operation of the burners 48a-h or 50 a-h, will have a injection of coke through pneumatictransportation with an elevated solids-air relationship and with aprimary air relationship of approximately 4% of the stoichiometric air.

A sixth outlet pipe 226 and a seventh outlet pipe 228 is connected withthe primary air blower 224. The sixth outlet pipe 226 being connectedwith fifth branch pipes 230, 232, 234 and the seventh outlet pipe 228being connected with sixth branch pipes 236, 238, 240. The exit end ofeach fifth and sixth branch pipes 230, 232, 234, 236, 238, 240, beingconnected in a direct way with each burner 48 f-to-h or 50 f-to-h. Theflow of primary air in each fifth and sixth branch pipes 230, 232, 234,236, 238, 240, are regulated individually by an arrangement of a firstglove valve 242, a first ball valve 244 and a second glove valve 246.

Additionally, the sixth outlet pipe 226 includes seventh outlet pipes248, 250 and 252, which are connected respectively with the fifth outletpipes 196, 198, 200. And, the seventh outlet pipe 228 includes sixthoutlet pipes 254, 256, 258, which are connected respectively with thefourth outlet pipes 190, 192, 194. Each sixth and seventh outlet pipes248, 250, 252, 254, 256, 258, having a check valve 260 and a ball valve262.

Through the arrangement above described, the primary air blower 224 willsupply primary air to the burners 48 f-to-h (left burners) or burners 50f-to-h through the sixth outlet pipe 226 and the seventh outlet pipe 228and by each fifth and sixth branch pipes 230, 232, 234, 236, 238, 240.The air blower 224 will operate to supply a maximum air flow during theoperation of each burner 48 f-to-h or burners 50 f-to-h, meanwhile aminimum air flow will be provide for the burners 48 f-to-h or burners 50f-to-h that are not operating by means of each sixth and seventh outletpipes 248, 250, 252, 254, 256, 258, to guarantee the better conditionsto be cooled.

Notwithstanding that the invention was described over the basis of threeburners 48 f, 48 g, 48 h and burners 50 f, 50 g and 50 h, should beunderstood that the system described in the present invention is appliedfor all the burners 48 a-to-h and 50 a-to-h.

In an additional embodiment of the present invention, the melting ofglass can be melted with two or three types of fuel, for example, inFIG. 3, the burners 48 a-48 d and 50 a-50 d can be fed with a pulverizedfuel as petroleum coke; and the burners 48 e-48 h and 50 e-50 h can befed with gas or fuel oil. In a third embodiment of the presentinvention, the burners 48 a-48 d and 50 a-50 d can be fed with apulverized fuel as petroleum coke; the burners 48 e-48 f and 50 e-50 fcan be fed with gas; and the burners 48 g-48 h and 50 g-50 h can be withfuel oil. These combinations are considering that at this date alreadyexists glass melting furnaces that uses gas or fuel oil as the main fuelfor melting glass, and that the behavior of said gas and fuel oil iswell known in the art.

Pulverized Fuel Burner

Additionally, for carrying out a good combustion of the pulverizedpetroleum coke, a special burner was designed to be used with the systemfor feeding and burning the pulverized fuel in the glass meltingfurnace. The FIGS. 7 through 12 shows a detailed view of the burner (48f) for feeding and burning a pulverized fuel in accordance with thepresent invention. The pulverized fuel burner (48 f) comprising a mainbody 264 constructed of an outer pipe 266, an intermediate pipe 268, anda inner pipe 270 (FIG. 10), which are disposed concentrically one withthe other. The outer pipe 266 being closed in the upper end 272 (FIG.9). A first chamber 276 is formed in the space defined by the outer pipe266 and the intermediate pipe 268. The outer pipe 266 having an inletpipe 278 and an outlet pipe 280 (FIG. 8) through which cooling water isintroduced in the first chamber 276 for the cooling of the burner (48f). The intermediate pipe 268 and the inner pipe 270 being extendedbeyond of the upper end 272 of the outer pipe 266.

On the upper part of the burner 48 f, an air inlet pipe 282 is connectedin a inclined form around the intermediate pipe 268, in order to beconnected with the sixth branch pipe 236 (see FIG. 7) for introducing aflow of primary air or natural gas in a second chamber 284 formed in thespace defined by inner pipe 270 and the intermediate pipe 268. Thesecond chamber 284 serves to direct the primary air or natural gas fromthe air inlet pipe 236 (FIG. 7) and is conveyed to the lower end of theburner 48 f. The flow of primary air in the second chamber 284 isregulated by the arrangement of the first glove valve 242, the firstball valve 244 and the second glove valve 246.

In the same way, a mixture of secondary air and pulverized petroleumcoke is introduced in an upper end 286 of the inner pipe 270 and isconveyed to the lower end of the burner 48 f. The upper end 286 of theinner pipe 270 is connected respectively with the fourth outlet pipe 194for feeding the supply pulverized fuel-secondary air mixture toward saidburner (48 f). So, when the primary air and the mixture of secondary airand pulverized petroleum coke reaches the lower end of the burner (48f), the primary air or gas natural and the mixture of pulverizedfuel-secondary air are mixed to ignite a combustion process, as will nowdescribed.

Making now reference to FIGS. 10 through 12 these are showing a detailedview of an embodiment of the burner (48 f) for feeding and burning apulverized fuel in accordance with the present invention.

Basically, the burner (48 f) [FIG. 10] comprises a main body 264constructed of an outer pipe 266, and a inner pipe 270, which aredisposed concentrically one with the other. A first chamber 276 isformed in the space defined by the outer pipe 266 and the inner pipe268. The outer pipe 266 having an inlet pipe 278 and an outlet pipe 280through which cooling water is introduced in the first chamber 276 forthe cooling of the burner (48 f).

Making now reference particular to FIGS. 10 and 11, the lower end 274 ofthe burner (48 f) includes a flow distributor 286 for receiving anddistributing the pulverized fuel and air or gas mixture. The gas beinggas natural or oxygen. The flow distributor 286 (FIG. 11) is connectedbelow the lower end 274 of the burner (48 f) and includes a main body288 defining a first distribution chamber 290 for receiving pulverizedfuel and air or gas mixture; and a second chamber 292 surrounding asection of the first distribution chamber 290 and a section of thesecond chamber 292 through which cooling water is introduced for thecooling of the burner (48 f).

The flow distributor 286 also includes a discharge end 294, located in a90° position with respect to the main body 288, in order to deviate theflow of the pulverized fuel and air or gas mixture from a vertical flowto a longitudinal flow. The discharge end 294 includes a passage 296(FIG. 10), which are formed longitudinally in the main body 286connecting the first distribution chamber 290 with the outer peripheryof said body 286. The passage 296 being formed by a first inner annularsection 298, through which flows the pulverized fuel and air or gasmixture. The first annular section 298 being internally formed in afrusto-conical form, with a diameter less in the front of each passage.And a second annular section 300 surrounding the first inner annularsection 296—through which pulverized fuel and air or gas mixture is madeflow. The first inner annular section 298 and the intermediate annularsection 298 defining en entrance for receiving a nozzle 302 to supplythe pulverized fuel and air or gas mixture-within the chambers of theglass melting furnace. Finally, the periphery of the main body 288 andthe second annular section 308 defining the third chamber 294 to makeflow water for the cooling of the burner (48 f).

Now making reference to the nozzle 302, this includes a cylindrical head304 and a cylindrical member 308 which is placed in coincidence with therear part of the head 304.

In a second embodiment of the burner (FIG. 11), the flow distributor 286is shown with two discharge ends 310, 312, located in a 90 degreesposition with respect to the main body 288. Nozzles 302, are introducedby each one of the discharge ends 310, 312. The position of thedischarge ends 310, 312, being separated with an angle approximate fromabout 10 degrees to about 20 degrees between each other with respect toa longitudinal axis 314.

Now, in accordance with the burner (48 f) shown in FIGS. 8 and 10 themixture of air or gas and pulverized petroleum coke is introducedthrough of the inner pipe 270 and is conveyed to the first distributionchamber 290 and from this section, the mixture flows into the passage296 of the flow distributor 286. The mixture is fed through the passage296 in an axial direction to be introduced into the chambers of theglass melting furnace.

Cooling water is continuously introduced through the first chamber 270and the third chamber 292 for cooling the burner.

Notwithstanding that the burner (48 f) has been described to be cooledwith water, it is possible to use a burner such as that disclosed theInternational Application PCT/MX2006/000094 by which the cooling bywater is not necessary.

In accordance with the above, a method for feeding and burning apulverized fuel in a glass melting furnace of type including a glassmelting region lined with refractory material and a plurality of burnersassociated in the glass melting furnace, the method comprising;

supplying a pulverized fuel of the type comprising fixed carbon andimpurity materials of sulfur, nitrogen, vanadium, iron and nickel ormixture of the same to each one of said burners in said glass meltingfurnace, said pulverized fuel being fed directly to the furnace in arelation fuel-air of about 16% of air in excess with respect to astoichiometric air;

burning said pulverized fuel by each one of said burners in the meltingregion of said melting furnace, providing a flame for each burner tocarry out a combustion process in said melting region for the melting ofthe glass;

controlling emissions of carbon and impurity materials produced by theburning of said pulverized fuel with environmental control means, saidenvironmental control means being located in a waste gas outlet of saidglass melting furnace, in order to clean the flue gases and reducing theemission of impurities from the pulverized fuel such as SOx, NOx andparticulates, said reduction of emissions being controlled during andafter that the combustion of the pulverized fuel in the glass meltingfurnace has been carried out; and,

counteracting erosive and abrasive effects of the pulverized fuel in theglass melting furnace by means of refractory means, said glass meltingfurnace being constructed with said refractory means for controllingsaid erosive and abrasive effects produced by the burning of saidpulverized fuel in said furnace.

The method also comprises the steps of:

feeding a regulated controlled flow of a mixture of pulverized fuel andair or gas under pressure for pneumatic transport in at least onedistribution means;

discharging the mixture of pulverized fuel and air or gas from feedingmeans toward at least one of said distribution means;

regulating in a controlled manner the pulverized fuel-air or gas mixturefrom the distribution means to each of a plurality of burners in a glassmelting region of the glass melting furnace;

burning said pulverized fuel by means of said burners in the glassmelting region of said glass melting furnace while providing acombustion flame with high thermal efficiency to carry out a controlledheating for melting the glass; and,

counteracting erosive and abrasive effects of the pulverized fuel in theglass melting furnace by means of refractory materials.

Additionally the method also includes the step of operating the burnersin alternate operating cycles between combustion and non-combustioncycles; also, returning the flow of pulverized fuel-air or gas mixturefrom the distribution means toward the feeding step while the alternateoperating cycle on the burners is carried out.

Environment Control

Finally, after of the combustion of the pulverized fuel in the glassmelting furnace has been carried out, an equipment for reducing andcontrolling the air pollution and emissions of sulfur, nitrogenvanadium, iron and nickel compounds at the atmosphere is placed at theend of the tunnel 44 and connected with the chimney 46 for the exhaustgases. The pollution control system according to the present inventionis adapted in a waste gas outlet of the glass melting furnace.

For the control of contaminant emissions, electrostatic precipitatorshave proven to perform well in the abatement of glass furnaceparticulate matter. The fine particulate matter of glass furnacespresents no problem for electrostatic precipitators.

In the case where SO₂ removal is needed in addition to particulatematter, a dry or partially wet scrubber makes a good complement to anelectrostatic precipitators or a fabric filter system. In fact, underthe conditions of high acid gas, a scrubber is necessary to reduce theconcentration of the corrosive gases. In the case of the use of a newfuel, a scrubber will be needed to lower SO2 content. It will not onlyserves as a benefit to the system for corrosion prevention, but it willalso lower the temperature of the exhaust and therefore reduce the gasvolume.

Dry scrubbing (the injection of a dry reactive powder) and semi-wetscrubbing will take place in a large reaction chamber upstream of theelectrostatic precipitators. In both dry and wet, the scrubbingmaterials will include Na.sub.2 CO.sub.3, Ca(OH).sub.2, NaHCO.sub.3, orsome others. The resultant reaction materials are basic ingredients tothe glass making process and therefore are generally recyclable up to apoint. A rule of thumb is that for every 1% of sulfur in the fuel, therewill be about 4 pounds of SO.sub.2 generated per ton of glass melted.So, for high sulfur fuels there will be an abundance of dry waste,NaSO.sub.4 for example. This amount of waste will vary with the capturerate and the amount of material that can be recycled, but the numberwill be significant. For the float furnace operating with high sulfurfuel there might be up to 5 tons of waste per day.

The performance levels of scrubbing vary from 50% to 90% using dryNaHCO.sub.3 or semi-wet Na2CO3. Temperature control is important in allscrubbing alternative with target reaction temperatures ranging fromabout 250° C. to 400° C. on the scrubbing material.

Wet scrubbers come in an almost infinite number of shapes, sizes andapplications. The two major applications, relating to glass making arethose that are designed to collect gases (SO.sub.2), and those that aredesigned to capture particulate matter.

From the above, a system for feeding and burning a pulverized fuel in atleast a burner of a glass melting furnace has been described and willapparent for the experts in the art that many other features orimprovements can be made, which can be considered within the scopedetermined by the following claims.

1. A method for the combustion of pulverized fuel as a heating sourcefor melting raw materials for producing glass, the method comprising: a)feeding a regulated controlled flow of a mixture of pulverized fuel andair or gas under pressure for pneumatic transport in at least onedistribution means; b) discharging the mixture of pulverized fuel andair or gas from feeding means toward at least one of said distributionmeans; c) regulating in a controlled manner the pulverized fuel-air orgas mixture from the distribution means to each of a plurality ofburners in a glass melting region of a glass melting furnace; d) burningsaid pulverized fuel by means of said burners in the glass meltingregion of said glass melting furnace while providing a combustion flamewith high thermal efficiency to carry out a controlled heating formelting the glass; and, e) counteracting erosive and abrasive effects ofthe pulverized fuel in the glass melting furnace by means of refractorymaterials, said refractory materials consisting essentially ofsilica-alumina-zircon, magnesite, chrome-magnesite, magnesia-aluminaspinel, alumina-silicate, zircon-silicate, magnesium oxide or mixturesof the same.
 2. The method as claimed in claim 1, wherein the refractorymaterials is a pressed silica.
 3. The method as claimed in claim 1,wherein the refractory materials is a fused silica.
 4. The method asclaimed in claim 1, wherein the refractory materials is a direct-castsilica.
 5. The method as claimed in claim 1, wherein the refractorymaterials is a fused-cast alumina-silica-zircon.
 6. The method asclaimed in claim 1, wherein the refractory materials is a pressedalumina-silica-zircon.
 7. The method as claimed in claim 1, wherein therefractory materials is direct-cast alumina-silica-zircon.
 8. The methodas claimed in claim 1, wherein the refractory materials contains about90-100% in weight of a fused-cast alumina.
 9. The method as claimed inclaim 1, wherein the refractory materials contains about 90-100% inweight of a pressed alumina.
 10. The method as claimed in claim 1,wherein the refractory materials contains about 90-100% in weight of adirect-cast alumina.
 11. The method as claimed in claim 1, wherein therefractory materials is a fused-cast magnesite-alumina spinel.
 12. Themethod as claimed in claim 1, wherein the refractory materials is apress magnesite-alumina spinel.
 13. The method as claimed in claim 1,wherein the refractory materials is a direct cast magnesite-aluminaspinel.
 14. The method as claimed in claim 1, wherein the refractorymaterials is a fused-cast magnesite-zircon-silica.
 15. The method asclaimed in claim 1, wherein the refractory materials is a pressedmagnesite-zircon-silica.
 16. The method as claimed in claim 1, whereinthe refractory materials is a direct-cast magnesite-zircon-silica. 17.The method as claimed in claim 1, wherein the refractory materials is afused-cast alumina silicate.
 18. The method as claimed in claim 1,wherein the refractory materials is a pressed alumina silicate.
 19. Themethod as claimed in claim 1, wherein the refractory materials is adirect-cast alumina silicate.
 20. The method as claimed in claim 1,wherein the refractory materials is a fused-cast zircon-silicate. 21.The method as claimed in claim 1, wherein the refractory materials is apressed zircon-silicate.
 22. The method as claimed in claim 1, whereinthe refractory materials is a direct-cast zircon-silicate.
 23. Themethod as claimed in claim 1, wherein the refractory materials is apressed direct bonding containing at least 98% of magnesium oxide. 24.The method as claimed in claim 1, wherein the refractory materials is adirect-cast containing at least 98% of magnesium oxide.
 25. The methodas claimed in claim 1, wherein the refractory materials is a presseddirect bonding containing about 90% and about 95% of magnesium oxide.26. The method as claimed in claim 1, wherein the refractory materialsis a pressed ceramic bonding contains between about 90% and about 95% ofmagnesium oxide.
 27. The method as claimed in claim 1, wherein therefractory materials is a direct cast contains between about 90% andabout 95% of magnesium oxide.
 28. The method as claimed in claim 1,wherein the refractory materials is a pressed direct bonding containingbetween about 5% and about 25% of chrome and between about 50% and about85% of magnesite.
 29. The method as claimed in claim 1, wherein therefractory materials is a pressed ceramic bonding containing betweenabout 5% and about 25% of chrome and between about 50% and about 85% ofmagnesite.
 30. The method as claimed in claim 1, wherein the refractorymaterials is a direct cast containing between about 5% and about 25% ofchrome and between about 50% and about 85% of magnesite.